A very easy way to do this is to check the host name:
rck00 -> core 0
rck01 -> core 1
rck47 -> core 47
If you need it within a C program then you can go ahead and read the configuration register.
I know I can get the core IDs if I want to.
My question is about whether the SCCLinux keeps any data or information about the current core ID within itself.
This will be better answered by someone in the know.
My guess is that it is not kept by the Kernel, because drivers (like rckmb: http://marcbug.scc-dc.com/svn/repository/trunk/linuxkernel/linux-2.6.16-mcemu/drivers/net/rckmb.c) read the configuration register to determine in which core they are running.